Unless you are absolutely certain he is faking, I wouldn't reject the possibility that he is having headaches ... it's not like a headache appears on a CT scan. (It's kind of surprising to me that a migraine sufferer would say "He has had a CT scan and it showed everything was OK for the scan of his brain, so he shouldn't be having 'headaches.') For example, tightened neck muscles can cause problems that manifest as headaches. My nephew suffered sudden headaches for years until he was prescribed muscle relaxers for his neck muscles. I'd keep trying various remedies for the headaches until you are convinced that they are being faked.
ahah so he gets a lot of attention from you when he has 'meltdowns' try being nonchalant ,not so concerned , see what happens ,Has he had any changes in routine , new sibling new teachers, new home ? sometimes changes can also upset them and they act out.Dont feed into the meltdowns , in fact let him have one , don't fight him over it, its a bit like us venting, we all do it.Good luck they are wonderful though aren't they LOl